This Phase II proposal is designed to provide and analyze a database which will largely delineate whether it is worthwhile to pursue a Phase III study of the CA 125 immunoradiometric assay (IRMA) as a component of strategy aimed at early detection and diagnosis of ovarian cancer in an at risk population. Specific objectives will include: (1) accurate determination of the specificity of the test for ovarian cancer used one time and serially in the study population of 5000 women aged 40 years or older, (2) determination of the nature of apparent false-positive results of this test, (3) identification of possible confirmatory tests which will improve the specificity of the CA 125 IRMA for ovarian cancer and (4) preliminary retrospective estimates of the sensitivity of the CA 125 IRMA for occult ovarian cancer. The principal endpoints of this study will be: (1) a plan to proceed to a prospective study of 50,000 or more women to determine accurately the sensitivity and positive productive value of the CA 125 IRMA and associated confirmatory and adjunctive tests for the early detection of ovarian carcinoma in an at risk population and (2) a collection of data allowing for determination of the cost- effectiveness of such a screening strategy. The results of this study should also provide a model for future evaluation of serum assays for such purposes and establish a well characterized serum bank available for evaluation of such assays.